The Israeli supreme court has doubled the sentence of an Israeli border police officer who shot dead an unarmed Palestinian teenager in 2014.

The ruling, announced on August 19, said the original nine-month prison sentencing of Ben Deri by the Jerusalem district court earlier this year did not adequately reflect the severity of his actions.

Deri admitted to shooting 17-year-old Nadeem Nuwarah in May 2014 during Nakba Day clashes between Israeli forces and Palestinian protesters in Betunia, south of Ramallah in the occupied West Bank.

The officer was found guilty of negligence by using live ammunition to disperse the protesters instead of rubber bullets, fatally shooting Nuwarah in the chest.

Deri had said during his trial he had mistakenly put live ammunition into his M-16 instead of rubber bullets.

The Times of Israel reported the judges verdict summary as they increased Deri’s sentenced to 18 months. “The sentence does not give sufficient expression to the value of the person’s life cut short by Deri, nor to the considerations underlying the obligation to respect the principle of purity of arms.”

“But more serious than that, was Deri’s intention to injure the deceased when he presented no threat to the force [at the scene]. And the result — death.”

A second teenager, 16-year-old Muhammad Abu Thahr, was also killed at the 2014 protests, but Israeli prosecutors found insufficient evidence to press charges.

The two killings were caught on CCTV, sparking outrage as the teenagers posed no serious threat to the Israeli soldiers.

Nuwarah’s father, Siam Nuwarah told Haaretz at the time they were not surprised with the initial verdict, saying his boy was “murdered in cold blood”.

“We are dealing with an entire system that discriminates on the basis of race and arrives at decisions that are far from just," Siam Nuwarah said.

According to Arab News, right-wing Israeli Zionist legal aid organisation Honenu, who represented Deri, said the supreme court’s ruling could “jeopardise the motivation and operational abilities of our soldiers.”

The Arab News article also quoted Defense Minister Avigdor Lieberman saying while Deri’s actions might have been wrong, “that doesn’t mean his punishment should be increased.”

The use of live ammunition by Israeli soldiers used to disperse protests has come under recent scrutiny by the international community, as the recent 'Right of Return’ protests along the Gaza border have resulted in 166 deaths by Israeli forces.

However in May this year, the Israeli supreme court unanimously rejected two petitions brought by human rights groups demanding Israel's army to stop using snipers and live ammunition against unarmed Palestinian protests in the Gaza Strip.